This invention relates to dental prosthesis such as crowns, bridges, or splints, and more particularly to a method and apparatus for removal of such prosthesis from teeth without damaging either the prosthesis or the teeth.
It is often necessary for a dentist to remove a crown or bridge that has been fixed in place on the teeth. For example, occasionally a problem arises in connection with the crown itself or the joining between the crown and the tooth. Leakage could occur, the crown could break or other things could occur. Occasionally, the crown must be removed for providing access to the teeth when further dental work is needed on the underlying teeth.
Another occasion requiring removal of the crown is when the prosthesis has been placed on a patient, especially on a young patient where the restoration is not necessarily one that will last a lifetime.
One method that has been utilized in the past is to cut a slice through the metal material on every abutment. This process is extremely time consuming and costly since the prosthesis is wasted. Another method has been to attempt to break the crown loose from the dental tooth using a mallet, chisel or the like. This procecure often fractures the tooth and is an extremely painful experience for the patient.
U.S. Pat. No. 3,747,215 describes another method which includes the casting of a sleeve directly in the crown. The sleeve is retained by means of laterally extending lugs which fit within the crown material. Internally of the sleeve is a threaded hole which receives a closure screw during actual utilization of the crown in the mouth. When removal of the crown is required, the closure screw is removed and replaced with a jack screw long enough to extend through the threaded hole within the sleeve so that it breaks the bond between the crown and the tooth as the jack screw is continuously threaded into the sleeve.
While this prior method is an improvement over prior art approaches, it requires that the crown be initially formed with the sleeve in it. Accordingly, it is not suitable for those situations where existing crowns are present in the mouth or where a crown has been prepared by a laboratory without the sleeve cast within it. Additionally, in most cases, the crown requires further adjustments upon installation in the mouth. Such adjustment frequently requires reduction in the occlusal anatomy of the crown during the fitting or seating process. With the sleeve cast within the crown and extending through the occlusal surface, it is not possible to reduce the occlusal height of the tooth since this would then destroy the ability of the sleeve to receive the closure screw therein. Also, the shape of the tooth anatomy is such that in many cases a crown must be placed on an anterior tooth, a posterior tooth, awkward shaped occlusal anatomies, etc. The sleeve could not be modified to accommodate an incline or angled upper surface. Also, using this method, a recessed area of the threaded portion necessitates a much larger system on the occlusal surface making it less aesthetic and requiring a flatter horizontal area. Also, it is difficult to obtain an absolute fit between the various portions of this system.
Accordingly, there is need for an improved method and appatatus for removing dental crowns. It should be appreciated, that hereinafter, the term dental crown will refer to all types of prosthesis capable of utilizing this system including crowns, bridges, splints, etc.